Rotor assembly air baffle



Dec. 3, 1963 D. MoRRls 3,112,915

ROTOR ASSEMBLY AIR BAFFLE Filed Dec. 22, 1961 INVENTOR DEE/'V 1026/5 2r-5 4 MM United States Patent O 3,112,915 ROTOR ASSEMBLY AIR BAFFLE Drew Morris, Cincinnati, Ohio, assiguor to General Electric Company, a corporation of New York Filed Dec. 22, 1961, Ser. No. 161,519 1 Claim. (Cl. 253-77) This invention relates to a rotor assembly and a rotor assembly air baille for use with a turbomachine rotor wheel and blade assembly.

In various turbomachinery designs utilizing arfoils or blades mounted around the periphery of a rotor wheel, it is important that the primary gas ilow pass only through the annular passage in which the vane portion of the blades are located, since any primary ilow leakage outside this annular passage severely affects the eillciency of the engine with resulting loss in thrust or power output. One primary area of diillculty in which gas leakage is a problem is around the shank portions of the blades lying between the blade platforms and the turbine wheel.

In addition to gas leakage, another diiliculty encountered in rotor assemblies of the. type mentioned is vibration between the rotor and blades and between the individual blades mounted on the periphery of the rotor. Various methods have been employed to prevent or damp this vibration, however these have generally involved the use of a heavy or complicated structure and costly components.

Previous attempts to add individual air bailles to the rotor and blade assembly have frequently resulted in unsatisfactory sealing, or the bailles which have been utilized are subject to failure or have not accomplished such other functions which may be performed by such a baille. The baille should present little aerodynamic drag on the rotor and in addition, if designed correctly can serve the useful function of damping vibrations between adjacent blades.

It is therefore one object of this invention to provide an easily assembled improved type air baille and blade assembly for a turbomachine rotor assembly.

It is another object of this invention to provide an improved air baille which effectively seals against gas passage, presents a minimum aerodynamic drag on the rotor assembly and serves to damp vibrations between adjacent blade assemblies.

Briefly stated, in accordance with one aspect of the invention, there is provided an air baille comprising end plates, one lltting on each side of the blade Shanks and facing in an axial direction, with a connecting member extending between adjacent Shanks to maintain the end plates in position. These plates are of configuration such that one baille may extend past at least two of the blade Shanks and abut the adjacent baille plates so as to present a substantially continuous annular Wall facing the gas stream which limits gas leakage and substantially decreases the aerodynamic drag on the rotor assembly while still allowing ease of assembly of the bailles and blades. In addition, the particular Wedging contact between adjacent blade platforms serves to damp vibration between adjacent blade assemblies and in this manner adds to the overall structural integrity of the rotor assembly.

The invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claim.

In the drawing:

FIG. l is a side view of the turbomachine rotor wheel assembly,

FIG. 2 is an enlarged perspective view of the air baille,

FIG. 3 is a side plan view of the air baille positioned in the phantom rotor assembly,

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FIG. 4 is a cross-sectional view of the air baille along the lines 4-4 of FIG. 3.

eferring now to FIG. l, therein is illustrated a turbomachine rotor assembly comprising a rotor wheel 11 with blades 12 attached thereto extending in a radial direction. These blades are attached in a Siamese twin fashion with two blades having bases extending into an opening 13 in the turbine wheel and forming a structure having corrugated sides corresponding to that opening so that the blades are retained from being thrown out in a radial direction. A locking strip 14 extends through the rotor wheel beneath the blades and is bent radially outward so that the end tab 15 overlies a portion of the rotor Wheel and the blades to maintain the blades in position on the rotor wheel. The blades consist of a shank portion 18 and a vane portion 19 with a platform 20 therebetween.

The blades iit together and are supported in the siamese twin manner illustrated to simplify the assembly on the rotor wheel and also to provide a self-damping effect to limit blade vibration during operation of the turbomachine. Vibration between the blades of a pair is damped by centrifugal force causing the blades to tend to move together due to the centers of support and centers of mass of the blades being oilset from a radial line so that a torque is applied on the blades of a pair to move the blades toward one another. This torque force causes the blades to move together and the platforms to contact thereby limiting vibration therebetween. This blade mounting assembly is more fully disclosed in U.S. Patent 2,990,156, Marshall et al., Blade Damping Means. It may be seen that by individually assembling the blades around the rotor in this manner a complete rotor assembly may be built up.

Viewing this rotor assembly as a whole, the normal primary gas ow would be normal and into the drawing in passing between the blade vane portions 12, however, it can be seen that some of this ow could leak or pass through the openings 26 between adjacent blades if this opening were not closed. To accomplish this, an air baffle 27 is provided as illustrated in FIGS. 2 and 4 with the phantom outline of the rotor assembly illustrated in FIG. 3. This air baille consists of end plates 29 and 30 with connecting members 31 and 32 extending therebetween. The special configuration allows the end plates to overlap at least two adjacent blade shank portions and extend between the rotor wheel and blade platform to provide a sealing Wall and prevent the axial passage of gas therethrough. The use of ilat end plates to form a substantially continuous wall to seal against gas passage substantially reduces the aerodynamic drag on the rotor structure when compared to structures having uneven surfaces facing the gas stream.

Referring back to FIG. l, the end wall 29 is shaped so as to abut the adjacent identical baille and wall so that the walls cooperate to form an annular wall substantially sealing against axial gas flow past the blade shanks. In a similar fashion, all of the end plates 30 cooperate to provide a downstream sealing wall. Also, the end Wall 29 has a cut out portion 33 to allow for the axial insertion of the final two blades on the rotor Wheel by allowing the baille to be assembled between the blades and the cornplete assembly of two blades of different pairs and the baille to be moved axially into position with the cut out portion 33 clearing the turbine wheel to allow for this insertion. As illustrated in FIG. 3, the connecting members 31 and 32 are iltted adjacent the platform and rotor wheels respectively to maintain the baille in the desired position illustrated.

The connecting member 31 is of a cross section to fit between the adjacent platforms 20 of blades of separate Siamese twin assemblies and be forced further in rubbing contact with these adjacent platforms by centrifugal force acting on the baille. The wedging action of the connecting member 31 acting against and between the adjacent blade platforms 2i) provides a more rigid and unified blade and rotor assembly. This Wedging action is aided by the centrifugal force acting on the baille which tends to force the connecting member 31 between the adjacent blade platforms.

Further, member 32 is of a general inverted V configuration to provide maximum support in two planes against forces acting normal to the baille end plates. @ne primary cause for such forces is the axial pressure caused by the primary gas flow acting on the end plate. Another cause for such a force is the interaction of the connecting member 31 and the blade platforms 20, as illustrated in FIG. 3, the platform 20 slants and is not normal to the blade axis, therefore centrifugal forces acting on the baille in forcing the connecting member against the blade platforms intersections results in an axially directed force on the baille toward the end plate 29. The end plate 30 is also made thicker to further resist this axial directed force.

It may be seen that when the air baille is positioned as illustrated in the drawings, it eilectively seals against the axial passage of gas past the blade Shanks. Another very important function served by the air baille is that while the Siamese twin blade assembly damps vibration between the blades of the assembly, the baille serves to damp vibration between adjacent assemblies by establishing a rubbing contact with blades of at least two assemblies and being forced into even greater contact by centrifugal forces acting on the baille. In this manner, the overall structural integrity of the rotor assembly is greatly enhanced in addition to sealing the rotor assembly against undesirable passage of gas therethrough.

While a particular embodiment has been illustrated and described, it will be obvious to those skilled in the art that various changes and modications may be made without departing from the spirit of the invention, and it is intended to cover in the appended claim all such changes and modiilcations that come within the true scope of the invention.

I claim: A rotor assembly for turbomachinery comprising the combination of a rotor,

a plurality of blades mounted around the periphery of said rotor, each of said blades having a shank portion adjacent said rotor and a vane portion with a platform therebetween, bailles to prevent axial ilow of gas between the shank portions of the blades having end plates fitting on the upstream and downstream sides of adjacent shank portions covering the opening between said shank portions, the adjacent blade platforms and said rotor, the end plates of adjacent bailles abutting each other to form substantially continuous annular walls, said plate members joined and maintained in said position by a pair of connecting members extending between said blade Shanks, with one of said connecting members wedging between said adjacent blade platforms to damp vibrations therebetween and said other member being of a two planed configuration to provide maximum support between said plate members.

References Cited in the ille of this patent UNITED STATES PATENTS 2,271,971 Doran Feb. 3, 1942 2,669,383 Purvis et al. Feb. 16, 1954 2,755,063 Wilkinson July 17, 1956 2,781,998 Barr Feb. 19, 1957 2,942,842 Hayes June 28, 1960 FOREIGN PATENTS 652,099 Great Britain Apr. 18, 1951 590,294 Canada Jan. 5, 1960 

